Fatigue testing machine



May 27, 1941.` F. BUCKINGHAM.

l FATIGUE TESTING MACHINE Filed April 11, 193s Y, 4 Sheng-sheet `1 Flg.

lNvENToR FBUCKINGHAM May 21, 1941. F. BUCKINGHAM 2,243,413

FTIGUE TESTING 'MACHINE Filed April l1. 1938 4 Sheets-Sheet 2 v INVENTOR 52 55 BUGKINGHAM Fl 7 BY f ATTORNEY May 27 1941 F. BUCKINGHAM 2,243,413

FATIGUEKTESTING MACHlNE Filed April 11, 195s 4 sneetsLsnee'` s INVENTOB F. BUcmNGHnM HTTOB May 27, 1941.- F. BUCKINGHAM FATIGUE TESTING MACHINE 4 sheets-sheet 4 Filed April 11, 1958 lOFm.

Patented May 27, l1941 EATIGUE TESTING MACHINE Francis Buckingham, Fra

or to The Baldwin nklinville, N. J., assign- Locomotive Works, a cor-r poration ot'lennsylvania Application Api-i111, 193s, serial Np. 201,42

This invention relates generally to material testing apparatus and more particularly to an improved fatigue testing machine.

Fatigue testing has always been of considerable importance, but-the machines applicable for 'such tests have been generally limited to standard sizes or shapes of specimens as well as being -dec'ient in certain operating character)- istics. It is desirable to test full size machine elements, especially in the automotive field,

whereinlconnecting rods and a large number of Y other parts'make up present-day automobiles. Such parts 'with their large variety of shapes and sizes involvecomplic'ations not only as to 'providing a single machine adapted for testing such parts but tn also effecting predetermined conditions of test such as speed and load. When the specimen begins to fail, the load will progressively decrease unless suitably adjusted. It is especially desirable to maintain the load constant throughout the test although under certain conditions of operation a variable load may be desired.

It is an object of my invention to provide an -im'proved reciprocating type fatigue testing machine together with improved means for determining the reciprocating load applied to the test piece. A further object is to provide imconstant load on the specimen as it progressively fails. To this "end, I have provided :lmproved means for adjusting the reciprocating stroke during operation of the machine and automatically in response to the loadon the test piece. n

`A further object is tc provide improved means for balancing the inertia forces of the reciproeating sensitive weighing elements of thev testing machine independently of inertia forces that A might exist in other reciprocating lload transmitting elements.

Another object is to provide an improved combination whereby positive mechanical pulsating forces may be transmitted either through the load weighing .system or Adirectly to the test piece without passing through the weighing system.

A still further object is to provide an improved compact and rugged together with having a high Fig. 2 is a transverse section taken on the line 2-2 of Fig. 1; l

Fig. 3 is a perspective View looking directly at the front of the machine in the direction of arrow A, Fig. 1, to show the specimen supporting tables and their range of adjustments;

Fig. 4` is a fragmentary perspective of the specimen supportingA table viewed in the direction of arrow B of Fig. 3;

line 5-5of Figs. 1 and 6;

Fig. 6 is a vertical longitudinal section taken' on the line 6 6 of Fig'. 5;

Figs. 7, 8 .and 9 are respectively transverse sections taken on the lines 1-1, 8-8 and 9 8 of Figs-5 and 6;

Fig. 10 is a transverse section similar to Fig. 2 v but showing a modied driving arrangement;

Fig. 11 is a. transverse section taken on line' II-II of Fig. 2;

Fig. 12 is a vertical axial section taken on line I2-I2 0f Fig. 11; f

Fig. 131s a diagrammatic outline of electrical and mechanical features of the load responsive control system. The specimen to be tested in ay be a standard test piece or any one of a large number of machine 'elements such as engine connecting rods proved means for maintaining a substantiallyr erally indicated at 2. I'his fixture is boltedv to a heavy plate 3 which is supported upon a heavy angle frame having a vertical portion 4 and a horizontal portion 5. The plate 3is provided with a series of T slots in its outer, upper and lower faces, while a series of T slots'in the fatigue testing machine that is relatively simple,

degree of sensitivity, accuracy, esse of addustment and adaptability to specimens of various shapes and sizes.

Other objects and advantages will be more apparent to those skilled in the art from the following description of the accompanying drawings in which:

Fig. 1 is a side elevation of my improved fatigue testing machine taken substantially on the line forwardly located` horizontal rib vertical and horizontal portions 4 and 5 permit plate 3 to be supported at various vertical and horizontal `positions or allow various parts to be secured directly to the angle frame. The angle frame is also longitudinally slidably supported upon a `heavy base 6 through suitable tongue and grooves i while the vertical portion' 4 has a slidable tongue and groove connection 8 with a main housing generally indicated at 9. The housing and base 6 nected together.

Mounted upon housing 9 ,is a reciprocating frame or head I0 carrying a weighing system, to be described, which is connected at Il to the upper end oi' specimen I. head Il causes the specimen to be valternately flexed as indicated by dotted'lines I2, Fig. 1. The reciprocating head speciilcally comprises a horizontally elongated frame having sides I3 andv I4, Figs. 5 and 6 to 9, cross-connected by a I5 and by intermediate and rearwardly located vertical ribs I6 Fig. 5 `is a horizontal section taken on the l are suitably rigidly con- Reciprocation of Y ure -the load thereon, a very heavy but slightly elastic weighing ring 21 has twol oppositely extending lugs respectively pivotally connected at 28 to side walls I3 and I4 and at 29v to a combined load transmitting and sensitive weighing Aunit generally indicated at 39, Figs. and 6.,

This unit is specifically shown ascomprising a multiplicity of rigidly connected parts including a bifurcated end section 3I to which pin 29 is connected and a specimen platen 32, said end section and platen being connected by a rod 33 one end of which is welded or otherwise suitably secured in platen 32 while the other end is bolted as at 34 to end section 3|. 'The specimen platen 32 is provided as shown in Fig. 5 with a pair of vertical T slots 35 for receiving suitable bolts for clamping a. specimen as shown at II, Fig..

1. To allow the sensitive unit 39 to be rigidly held against lateral or vertical movements relative to thereciprocating head I3, I4, I5, etc., but at the same time allow said sensitive unit to have complete freedom ofmovement in a longitudinal direction relative'to the reciprocating head, there .is provided two flexible stay plates 36 and 31 which are relatively wide in a transverse direction as shown in Fig. 5 and are l relatively thinalthough preferably tapered from their mid-sections toward their ends as shown in Fig. 6. The .lower ends of these stay plates are rigidly held by bolts and keyways generally in.

dicated at 38 to a plate 39 which in turn is securely fastened to cross-rib I5. The upper ends of the stay plates are bolted as at 40 to the specimen platen 32 and to an upstanding portion 4I of the bifurcated end section 3l, This sensitive unitvis thereby firmly held against any movement normal to the axis of rod 33 but is free to have longitudinal movement which is maintained on a horizontal axis at all times by the action of stay plates 36 and 31 which will flex to maintain the eifect of a parallelogram. The flexure of the stay plates is very minute ink actual operation as will be seen shortly.

Under certain conditions it isv `desirable to eliminate the'weighing operation which is done by clamping the sensitive unit 39 to the reciprocating head, thereby preventing. any relative .1

is transmitted from connecting rod 24 to the side walls I3 and I4 and thence through bushings 45 to tie rod 33, therebyI shunting the load around weighing ring 21 to render the same inoperative. i

ITo determine the loading force transmitted to a specimen, bolts 43 are loosened whereupon bushings 45 will either work away from or be sufficiently, free of atted surfaces 48 to allow the sensitive unit 39 to move relative to the reciprocating head. In this case loading forces are transmitted from connecting rod 24 through pins 25 and 28 and thence through weighing ring 21,

pin 29 and sensitive unit 39 tothe specimen clamped to platen 32. The loading force causes elastic ring 21 to be deformed in proportion' to the force transmitted therethrough. The deformation of ring 21 is measured by a suitable strain gauge generally indicated at 59 disposed within and engaging the opposed walls of the hollow interior of ring' 21.

To obtain maximum accuracy of the load force transmitted to the specimen, it is necessary to compensate for the inertia forces present in th'e sensitive unit 39 but any such compensation must not interfere with .the sensitive and minute longitudinal mbvements of the unit 39 relative to the reciprocating head. To accomplish this, I have provided as shown in Figs. 1 and 6 an inertia compensating arm 52 extending vertically down within housing 9 and pivotally supported as at 53 between aide walls I3 and I4 of head I9 while the upper end of said arm is disposed in the bifurcation of end section 3| and pivotally connected thereto as at 54, Figs. 5 and 6. A slot 55 is formed in the upper wall 56 of housing 3 through which the compensating arm 52 extends. A weight 51, Fig. 1, is supported on the lower end of arm 52 and is of any suitable mass as may be variously determined in accordance with the size of the specimen being tested inasmuch as the inertia of the specimen has some effect upon-the sensitive unit 39 by virtue of being rigidly-secured thereto. The compensating arm 52 reciprocates bodily with reciprocating head I9 and hence any tendency of the momentum or inertia of sensitive head 39 and of the specimen is counmovement between the sensitive unit and they reciprocating head. providing, specifically, a pair of bolts 43 extending transversely through the forward ends Aoi' side walls I3 and I4 and through slightly enlarged openings 44 in tie rod 33. Bushings 45 surround one end of bolts 43 and are formed inagainst ilatted surfaces 48 on tie rod 33. The

sensitive head is thereby immovably held to side walls I3 and I4 so that reciprocating movement This is accomplished by terbalanced by a similar inertia or momentum created by weight 51. These inertia or momentum forces oppose each other by .virtue of the respective forces acting on opposite sides of the I pivot pin 53. l

Stroke adjusting mechanism-It is desired to maintain a substantially constant load on the specimen from the beginning of the test on through to failure of the specimen. If the stroke of the reciprocating head remains constant during progressive failure of the specimen, then the specimen offers less resistance to movement and accordingly the load applied decreases.- This can be compensated for only by increasing the stroke when and as the load tends to decrease. To increase the stroke during operation of the machine. crankpin 26, Figs. 1 and 2, is formed rigidly With a slide block 59 which is guided in a radial guideway 6I. This guideway is formed rigidly withv a relatively heavy flywhee1 62 and The flywheel is secured toa drive shaft 53 supported by bearings 64 of a suitable framework 65. To radially adjust crank 25, a screw 58 has threadedengagement with block39 and is supportedin a'bearing 61 secured to the face of flywheel 62. The lower end 68 of the screw is -provided with a square wrench end for manual adjusting or assembling purposes. fA suitable A thrust collar 69 secured to screw 69 engages one side of bearing 91 while 'the hub of a worm gear engages the other side of said bearing, thereby to hold the screw against axial displacement. To rotate the screw, a worm 1| engages worm gear 10 and is mounted on a shaft 12 Journalled .in the flywheel. Means for rotating the worm shaft 12 is specifically shown herein as comprising. a'. star wheel 13 secured to shaft'12. To rotate' the'star wheel in response to predetermined load conditions, such asa decrease in load below a predetermined value, a solenoid 14 is secured to framle 55 w ereby upon energization of the solenoid its pl ger 15 is moved upwardly into the path of star wheel 18 and hence during the'sucfor controlling energization of solenoid 14 in accordance with load transmitted through weighing ring 21 will be described hereinafter.

x cessive revolutions of the flywheel, the star wheel nalled in a suitable bearing 99 which is formed with or secured to a horizontal wall of frame 85.

' This low speed is useful not only for initially ad- .justing the machine or during a low speed test-but `.also for starting the machine when a heavy load is -to be' suitably applied to a specimen followed by a' .subsequent high speed of operation. In this latter casethe clutch 94 is initially engaged to start movement of the reciprocating and rotating masses and then the clutch lever` 91 is moved downwardly to quickly engage vthe high speed clutch |0I. In the modiiication of Fig. 10, the crankshaft 88' is drivenat all times directly from the motor |08 through belts 88,. A generator |09 is connected to motor |.08 to provide electrical current at a desired voltage for the load responsive control apparatus although' inlthe preferred form of Fig.

15 will drop by gravity or be biased by a spring out of the path of the star wheel. The means Driving mechanism-Shaft 63 is driven by an electric motor 80 and variable speed reducing gear mechanism 8|, both disposed in the bottom of housing 9, through pulleys 82 and 84 connected by afbelt 83. Pulley 84 is. secured to a sleeve 85 journalled in housing 9 and in frame 55 by a bearing with a shaft 89- supported in frame 65 by bearings 90 86. Sleeve 85 has a gear 81 meshing and 9|. Gears 92 and -93 are respectively keyed to theshafts 89 and 63k while a dog clutch 94 is slidably splined to shaft 89 forV engagement with cooperating clutch teeth 95 on gear 88. To obtain slow speed rotation 'of flywheel 62, a pivoted bellcranlr` hand lever 91 is moved downwardly thereby causing clutch shifting ngers and shaft generally indicated at 98 to engage clutch 94 with clutchteeth 95 and simultaneously cause an operating rod 99 and lever |00 lto -throw a clutch |0I out of engagement. As a result, power is transmittedi'rom pulley 82 through belts 83,

pulley 84,v sleeve 85, gears 81, 88, shaft 89, gears 92 and 98 to rotate crankshaft 83. To eiect 2, th'e load control supply current is obtained,

exciting coil ||0 mounted in a framework and a' pair of inductance coils ||2 supported on each side oi' coil |I'0 ina suitable frame H3. The

two coil frames are attached to the inner Aperiphgearv88 ,which is idly .iournalled on a .highspeed retenedor the crankshaft, the bencrank lever 91 is moved to its as shown in Fig. 2 thereby disenga'gingclutch 94 and engaging'clutch |0|, whereupon pulley 84 is directly connected to crankshaft 63 to enect high speed rotation thereof. To obtain inter'- msediate speeds, the variable speed transmission 8| of any suitable and well-known type can be adjusted by e hand wheel |03 connected te e shaft |04 and chain |05. Details of construe` tion of this speed change transmission per se do not form a part of my present invention and hence further description thereof is not deemed necessary.

nected, in its movement to the left, through a uppermost positionl ery of -the weighing ring at opposite points thereof and in longitudinal alignment with pivot pins 28 and 28-whereby any deformation of the weighing ring will cause relative rectilinear movement between the eld coil I0 and-the inductance coils ||2. The coil ||0 is normally in a neutral position between the coils' I2 when the weighing ring 21 is not under load. Hencel the coils H2 Vwill respond either to a compression or tension force applied to the' weighing ring. The exciting coil is normally supplied with current throigh wires ||5 and |I6 from a suitable A. C. source `||4. `A' supply switch ||1 and an 'adjustable rheostat ||8 and voltmeter -||9 are provided. The two colls` H2 are connected in series with each other and with a rectier |20, the direct current side of which is connected to an oscillograph vibrator I2 -A usual oscillatable mirror diagrammatically indicated at |22 is adapted to reflect light from a source lamp |28, toa photoelectric cell |24. 'I'he lamp' |28 is energized from the main supply line'- 5, while the photoelectric cell is connected to any suitable or usual photoelectric relay, dlagrammatically indicated at |25.

The strain gauge 50 is the only load control element forming a part of the reciprocating head of theV machine; all other control elements being located either von the stationary part of the machine orin a suitable cabinet as maybe desiredv with wires leadingthereto from the strain gauge.

, The remaining control elements and the circuits therefor will be readily understoodpfrom the following description of the mode of operation there- Assuming'that the machine isoperating with the reciprocating head I0 imposing. a relatively spring 99a, Fig. l12, to arms 991` and 99e of the 75A small load on the specimen below the desired preclutch shipping mechanism 98, Fig. 11. .Movement determined load value. To automatically increase the stroke of the testing machine and thereby increase the load on the specimen, the operator momentarily closes .a normally open load control starting switch |30 whereupon current is supplied from main line ||5 through a rectiiier |3| and thence through wires |32 and |33, a holding circuit relay |34, switch |30 and wires |35 and |33 to the other side of rectifier |3|. Energization of holding relay |34 causes switches |31 and |33 to be held closed. These switches are mechanically connected to, but insulated from, each other. A loading relay circuit is now energized to supply current to the star wheel solenoid 14. This circuit is supplied from main line 5 through rectiiler |3|, wires |33, |40, relay switch |33, star wheel relay |4|, wires |42 and |43 to switch |44 closed by a suitable spring and thence through wires |45 and |32 to the other side of rectifier |3|. Closure of relay switch |43 supplies current from the main line ||5 through wires |41 to energize solenoid 14 and accordingly move plunger 15 into the path of star wheel 13 to cause screw 33 to increase the stroke of reciprocating head I0. The solenoid plunger 15 will remain in the path of the star wheel so as to continually increase the stroke and load onthe specimen. When the desired load is finally obtained, the weighing ring 21 will be sumciently strained to cause coils and ||2 to transmit current impulses of suiiicient magnitude to oscillograph |2| whereby mirror |22 will be oscillated so as'to direct a beam of light |21 on to photoelectric cell |24. Energization of photoelectric cell |24 causes current to flow from supply wires through rectier |3| and thence through wire |50, relay |25-, and wire |5| to a time relay |52v and wire |53 to the other side of rectier |3|: 'Iime relay |52 thereupon opens switch |44 to break the circuit through the load feed relay |4 The solenoid plunger 15 thereupon withdraws frm the path of star wheel 13 toallow the crank stroke to remain ilxed. Y

The alternate tension and compression loads transmitted from the reciprocating head l0 through weighing ring 21`will cause coils ||0 and ||2 to produce a pulsating current passing from one extreme value through zero to the other extreme value., These pulsations will vary in accordance with the speed of rotation of crankshaft 23 and as a result the oscillograph mirror |22 will cause the light beam to be moved on to and olf of the photoelectrlc cell |24 with Ythe same frequency. Inasmuch as it is not desired to have the stroke further adjusted so long as the light beam is able to strike the photoelectric cell, the time relay |52 is operative to bridge over the momentary periods of deenergization of the photoelectric cell which occur with each stroke. This bridging is accomplished by providing a condenser |54'. and an adjustable discharging rheostat |55 in a parallel circuit across relay |52. This parallel circuit is closed by a switch |54 insulated from but meohanically connected to switch |44 whereby switch |54 is closed when switch |44 opens. During the successive instants that the pohtoelectric cell is deenergized, current will not be supplied through wires |5| and |32 to the time relay |52, but the condenser |54' discharges' to energize relay |52 and thereby maintain switch |44 open so as to prevent reclosure of the load feed relay |4|. The resistance |55 is adjusted in accordance with the predetermined value on each stroke of the reciprocating head thereby to reenergize the photoelectric lbell, or provided that the desired load recurs before expiration ofthe time at which the time relay is set to open. In case the load decreases so that the light beam fails to strike the photoelectric tube |24 within the time interval set for the time relay |52, then the time relay will Y be deenergized to allow switch |54 to open and switch |44 to close, thereby reestabli'shing a circuit for load feed relay |4| whereupon the star wheel solenoid 13 is energized to cause a further increase inthe stroke. Whenthe desired load is reestablished, the solenoid circuit is opened as previously described.

To discontinue the automatic load control, the

operator merely momentarily opens the normally .closed stop switch |53, thereby opening the holding circuit for solenoid |34. Switch |33 thereupon opens to break the control circuits. To provide a maximum limit for the stroke of the reciprocating head |3, a limit switch |53 is placed on the upper portion 53 of housing 3 to be engaged by a suitable cam projecting-laterally from side I3 of the reciprocating head |0 thereby to open switch |53 when the reciprocating head has a predetermined maximum stroke. This limit switch opens the holding circuit 'for relay |34 and shuts down the automatic stroke control circuits in `the same manner as was done by opening of stop switch |53. `i

To adjust the predetermined load value at which it is desired to operate the machine, the position of photoelectric cell |24 can `be laterally adjusted in any suitable manner. As dia- -grammatically shown the cell is mounted lupon a suitablerectilinearly movable frame adapted to be shifted by manual rotation of a screw |30. For low load values the cell |24 is4 shifted to the left and for higher loads itis shifted to the right.

vOperation.- 'I'he angle frame 4, 5 is adjusted along guideways 1 and 3 to any desired transverse position and plate 3, if used, is suitably located and supported upon the angle frame, all for the purpose of accommodating and anchoring one end of any suitable machine part or specimen such as diagrammatically indicated at Fig. l.

`The upper end of the specimen is then secured to reciprocating platen 32. Bolts 43 are loosened and thereafter crankshaft 33 is initially rotated at a slow speed by motor 30. The crank throw 23 has been previously manually adjusted by application of a wrench to the lower end of screw' 33, thereby to cause connecting rod 24 to impart a predetermined extent of reciprocation to head |3. The loading force is transmitted through weighing ring 21 to sensitive unit 30 and thence to the free end of the specimen to cause alternate deflection thereof on opposite sides of its neutral axis if alternate compression and tension stress,- ing is desired. However, if desired, compression stressing only, or tension stressing only, may be obtained merely by fastening the specimen in an unstressed condition to reciprocating head |0 the speed at which'the machine is operated so that the time relay switch when the latter is at the extreme end of its forward or rearward stroke. The load imposed upon the specimen causes elastic weighing ring 21-to be deformed, the extent and direction of deformation being an indication of the magnitude and character of load transmitted. This deformation is measured by a strain gauge 50 which initiates operation` of the stroke control system above de scribed. During the reciprocation of head I0, sensitive unit 33 is maintained in parallelism with the base of the machine by virtue of stay plates 33 and 31 which plates firmly resist any lateral or distortional movements of the-sensitive unit and weighing ring 21. Inertia`of the specimenv Vand sensitive unit 3l is counterbalanced by arm 52 and weight' l1 shown in Fig. 1. When the specimen begins to fail, and as it continues to progressively fail, the strain gauge il causes solenoid 'I4 to move solenoid plunger 'Il into-the path of star wheel 13 during rotation of ilywheel 62, thereby to rotate screw I3` and eect radial outward movement of crankpin block 3l to increase the stroke and thereby maintain a substantially constant load on the specimen. This is continuedgup to the point/of specimen failure. If it is desired to eifect h/igh speed operation or ii' the repeated stresses in the specimen will be of a very large number before failure startathen bolts 43 are tightened to cause bushing 4 5 to firmly' clamp tie rod 33 -to the side walls I3 and i4 to reciprocate as an integral unit therewith. During this operation the weighing ring 21 is inoperative. the load forces being transmitted from connecting'rod 24 through the side walls i3 and I4 to bushings 45 and tie rod, 33 to platen 32. In this operation the apparatus can be driven at a very high speed with minimum wear and tear on the apparatus. The bolts 43 may be loosened or tightened while the machine is operating under its slow speed of say 5 or 10 strokes per minute.

From the foregoing disclosure i-t is seen that'I have provided an extremely rugged, compact and yet highly sensitive and accurate fatigue Jaesting machine adapted to maintain a substantially constant load on a specimen from the beginning of a changes in details of-construction and arrangement of parts may be made by those skilled in the art without departing from the spirit of the invention as set forth in the appended claims. v -I claim:

1. A fatigue testing machine comprising, in combina on, means for supporting a specimen,

a reciprocable element connectable to the speci- 'V men, mechanical actuating means for continufously recipro/c'ating said element to eiect re'- l peated stress applications to the specimen, de-

formable loafd weighing means connected to and between saidelement and said actuating means so as to be bodily reciprocable with said element whereby'actual load forces are transmitted at 4each instant through said deformable weighing means to the specimen, and means connected toI and directly actuated by the deformation of said l load weighing means thereby to determine the actual load applied to the 'specimen independently of movements of the specimen.

f2.1A fatigue testing machine comprising, in

test to the end thereof, this being accomplished to the specimen at each instant during continuous reciprocation'of said element including an elastic load weighing ring and` strain responsive means directly connected to and operated by the opposite sides oi said ring.

3. A fatigue testing machine comprising, inl

combination, means for supporting a specimen, a reciprocable element connectable to the specimen, actuating means for continuously reciprocating said element to ene'ct repeated stress application to the specimen, deformable load weighing means interposed between said actuating means and said element and connected to each of the same for bodily reciprocation therewith whereby load is transmitted from said actuating means through said weighing means to said element throughout the full range of specimen loading, and means connected to and directly actuated` by the deformation of said load weighing means independently oi' movement of said specimen.

4. The combination set lforth in claim 3 further characterized in that said interposed weigh-v ing means comprises a weighing ring and strain responsive means connected to and operated directly by the opposite sides oi said weighing ring for determining the load transmitted therethrough.

men load for automatically adjusting the 'crank throw. I

6. A fatigue testing machine comprising, in combination, means for supporting a specimen, a reciprocable element connectable to the specimen, actuating means for-reciprocating said element, mechanism for varying the length of stroke of said reciprocating element, and means for operating said stroke adjusting means automatically in response to load transmitted to the combination, means for supporting a specimen,

a reciprocable element connectable to the specimen, actuating means for continuously recipro- -cating said element toeiect repeated stress application 'to the specimen,v and means connected to and between said element and said actuating means so as to be bodily, reciprocable with said 'element fordetermining the actual load applied ment, and means automatically responsive to the actual load transmitted to a specimen for maintaining a substantially constant load on the specimen by varying the length of the reciprocating stroke of said element. y

8. A fatigue testing' machine comprising, in combination, means for supporting ,a specimen,

.a reciprocable element connectable to the specimen, mechanical means rotatablev at a constant speed forL reciprocating said element, mechanism for determining the actual load on the specimen Eto impose a load on the specimen, load weighing means, means for transmitting loa'd from said actuating mechanism through said weighing means to the specimen, and means alternatively operative to shunt said weighing means and shunt said weighing means while said weighing means remains connected to said reciprocable element and to said actuating means.

11. A fatigue testing machine comprising, in combination, means for supporting and rigidly anchoring one end of a specimen, a reciprocable head, actuating means connected to said head for reciprocating the same, a combined load v transmitting and sensitive load weighing means entirely supported by said head for bodily reciprocating movement therewith as a self-contained part thereof and operative to have movement relative thereto, and means for rigidly securing the other end of the specimen to said l combined load transmitting and sensitive weighing means.

' 12.l The combination set forth in claim 11 further characterized 'in that said combined load transmitting and weighing means includes a sensitive unit, and flexible stay plates for supporting said unit by said reciprocating head.

' tending to produce any further adjusting action.

17. A fatigue testing machine comprising, in combination, a base having a guideway, a frame slidably supported on said guideway, means connected to said frame for reciprocating the same.

specimen engaging means, means connecting said specimen engaging means to said -frame so as to reciprocate therewith and to have movement relative thereto, and a load weighing ring connected at one of its sides to said reciprocating frame and at its other side to said specimen engaging means whereby' said frame together with said weighing ring and specimen engaging means allcomprise a self-contained reciprocating unit.

18. A fatiguey testing machine comprising, in combination, a base having'a guideway, a reciprocating frame slidably supported by said guideway, a connecting rod pivotally connected to one end of said frame for reciprocating the same, specimen engaging means positioned at the other end of the frame, means for supporting said specimen engaging means directly on said lframe so as to have bodily reciprocating movement therewith and to` have movement relative thereto in the ldirection of reciprocation, and a load weighing ring movably connected at one end to said frame and at its other end to said specimen engaging means.

13. A' fatigue testing machine comprising, in K combination, means for supporting a specimen, a reciprocable head, actuating means connected to said head for reciprocating the same, a sensitive weighing unit supported by said head for bodily reciprocating movement therewith and operative to have movementmelative thereto, said weighing unit having inertia eects arising from' said reciprocating action and said inertia `efIects tending to produce 'undesirable movement of the sensitive weighing unit relative to said reciprocable head, means ior securing a specimen to said sensitive weighing unit, and means movable relative to and also bodily movable with said head and connected to said sensitive weighingv unit for counterbalanclng said inertia effects thereof arising from said reciprocating movement.

14. A fatigue testing machine comprising, in l combination, means for supporting a specimen, a reciprocable element connectable to the specimen to impart a pulsating load thereto, actuating means for reciprocating said element, means for adjusting the extent of reciprocation of said element, means for determining the load applied to the specimen including a photoelectric cell, and means associated with said cell for con'- trolling said adjusting means to maintain a predetermined load on the specimen.

15. The combination set forth in claim 14 further characterized by the provision of means for causing said associated means tomaintain a stabilized condition so long asa given series of pulsating loads reach a'predetermined value. 16. A fatigue testing machine comprising, in

combination, means for supporting a specimen, a

19. 'Ihe combination set forth in claim 18 further characterized in that said .means for movably supporting the specimen engaging means on the reciprocating frame includes a horizontal member interposed between the specimen engaging means and said weighing ring, a plurality of parallel stay plates having their corresponding ends connected respectively to said reciprocating frame and to said horizontal member to insure said relative movement thereof in a direction parallel to the direction of reciprocation of said frame.

20. A fatigue testing machine comprising, in combination, means for rigidly anchoring one end of the specimen, a reciprocating element connectable to the other end of the specimen, actuating means for reciprocating said element; mechanism for varying the stroke of said reciprocating element, load weighing mechanism responsive to the actual load transmitted to a specimen, and means operated by said weighing means for controlling said stroke adjusting mechanism thereby to maintain a substantially constant load on the specimen as it progressively fails.

2l. A fatigue testing machine comprising, in combination, means for supporting a specimen, a reciprocable element connectable to the speci men to impart a pulsating load thereto, actuating means for reciprocating said element, means for adjusting the extent of reciprocation of said element, mechanism for determining the load applied to the specimen, means associated withsaid mechanism for controlling said adjusting means to maintain a predetermined loading eect on the specimen, and means for maintaining a stable position oi' adjustment of said adjusting means so long as a given series of pulsating loads reach a predetermined value.

FRANCIS BUCKINGHAM. 

